Process for recovery of aluminum chloride

ABSTRACT

Method for directly desubliming gaseous aluminum chloride to solid form in a fluidized bed of solid particles of aluminum chloride at controlled temperatures for production of selectively constituted solid particulate aluminum chloride.

This application is a continuation of application Ser. No. 567,506 filedApr. 14, 1975 (now abandoned) which application was a continuation ofour earlier application Ser. No. 392,569 filed Aug. 29, 1973 (nowabandoned) which application was division of our earlier applicationSer. No. 180,277 filed Sept. 14, 1971 (now abandoned).

This invention relates to the production of aluminum chloride, and moreparticularly to an improved method for effecting the condensation ofgaseous aluminum chloride to a selectively constituted and advantageoussolid form in a fluidized bed of solid particles of aluminum chloride.

Although the potential advantages of utilizing aluminum chloride as asource material in the electrolytic production of aluminum have longbeen recognized, commercial realization thereof has been precluded bythe inability of the art both to provide aluminum chloride ofsufficiently high purity as to be utilizable therein and to providealuminum chloride in any significant required quantity therefor in aneconomically acceptable manner. The long standing incentive and need foreconomically producible high purity aluminum chloride has resulted inextensive experimental exploration and evaluation of numerous suggestedexpedients for obtaining such long desired result. However, to date noneof these suggested expedients has succeeded in satisfying the desiredobjective of commercial quantity production of economically produciblehigh purity aluminum chloride.

In general, the reduction of aluminum-containing materials with chlorinein the presence of reducing carbon in some form to produce aluminumchloride is an old and generally well-known reaction. Such reactionproceeds vigorously and usually results in the provision of aluminumchloride in gaseous form in the elevated temperature gaseous effluentthereof.

One of the problems heretofore faced by the art has been the efficientand economical separation and recovery of such aluminum chloride valuesfrom the reaction effluent and, in particular, the actual separation andrecovery of the produced gaseous aluminum chloride in readily usableform by condensation techniques has proved particularly troublesomebecause of the inherent characteristics of aluminum chloride during thecondensation operations, and especially because of the influence of thevapor pressure of aluminum chloride on the degree of condensation underambient conditions.

The invention may be briefly described as a process for the efficientand continuous recovery of selectively sized and contoured aluminumchloride from an essentially contaminant free gaseous effluentcontaining such aluminum chloride, chlorine, phosgene and carbonmonoxide emanating from the chlorination of alumina by the directdesublimation of such gaseous aluminum chloride in a self-replenishingfluidized bed thereof maintained at a predetermined temperaturesubstantially below the upper ambient solidification temperature ofaluminum chloride.

Among the advantages of the subject invention is the permittedeconomical and efficient recovery of aluminum chloride from the gaseouseffluent emanating from the chlorination of alumina containing material;a permitted commercial quantity production of aluminum chloride and theproduction of selectively sized and contoured particles of aluminumchloride of advantageous character and which is particularly suited forthe electrolytic production of aluminum therefrom.

The object of this invention is the provision of an efficent andeconomical process for the continuous commercial quantity production ofselectively constituted aluminum chloride from the residual hot gaseouseffluent of the chlorination of alumina.

Another object of the invention is to provide an improved process forthe continuous commercial quantity production of solid particles ofaluminum chloride that, because of its readily handleable and flowablecharacter, is particularly well suited for direct utilization in theelectrochemical production of metallic aluminum.

It is a further object of the invention to provide an improved processfor carrying out the direct desublimation of gaseous aluminum chloridein a fluidized bed maintained at a temperature substantially below theupper ambient condition solidification temperature of aluminum chloride.

A further object of this invention is the provision of improved processof effecting the selective introduction of the gaseous aluminum chloridesubstantially without loss of heat into a fluidized bed of particles ofaluminum chloride remote from all contact surfaces to localizedesublimation thereof on the particles of the fluidized bed material.

A still further object of this invention is the provision of solidselectively sized particles of aluminum chloride of generally lobularcontour and characterized by the effective absence of planar exteriorsurfaces and relatively sharp protuberant angles.

Other and further objects of the present invention will become apparentfrom the within specification and from the accompanying drawing whichillustrates the principles of the invention as embodied in certainpresently preferred apparatus elements therefor, in which:

FIG. 1 is a schematic representation of apparatus elements utilizable inthe practice of this invention.

FIGS. 2a, 2b and 2c are photomicrographs, at 30, 200, and 500magnifications respectively, illustrative of the selective configurationof a preferred product obtained through the practice of this invention.

FIGS. 3a, 3b and 3c are photomicrographs, at 30, 200 and 500magnifications respectively, illustrative of the selective configurationof a smaller sized product obtained through the practice of thisinvention.

In accordance with the principles of the present invention, a processfor the efficient and economical commercial quantity recovery of solidaluminum chloride of advantageous physical character from a gaseousaluminum chloride-containing carrier, such as the residual hot gaseouseffluent of the chlorination of alumina, is now provided. Includedtherein is the selective desublimation of gaseous aluminum chloride in afluidized bed of particles of aluminum chloride maintained at attemperature substantially below the upper ambient conditionsolidification temperature of aluminum chloride. Such desired operatingtemperature of the fluidized bed will range between 30°-100° C.,suitably within about 60°-90° C. and preferably within the range ofabout 50°-70° C. "Desublimation" as utilized herein refers to the directformation of solid aluminum chloride from the gaseous phase thereofwithout any noticeable formation of an intermediate liquid phase.

The described desublimation of the aluminum chloride can be carried outat negative or vacuum pressures, e.g. down to about 0.1 atmosphereabsolute, as well as at positive or elevated pressures, up to thepressure at which aluminum chloride would condense as a liquid underambient conditions, subject to considerations of partial pressure of thealuminum chloride present under the ambient conditions. A preferredoperating pressure is about 1.5 atmospheres gauge.

In the practice of the invention, any relatively pure gaseous aluminumchloride-containing gaseous carrier from any convenient source can beutilized as a source material. Suitably, a gaseous effluent of the typeobtained from a precursor chlorination of sodium contaminated alumina inthe presence of carbon and from which concomitant entrained particles ofsolids and liquids and condensable volatile constituents or impuritieswhich condense at a higher temperature than the upper condensationtemperature of aluminum chloride under the corresponding ambientconditions have been preliminarily removed, is preferably employed asthe desired relatively pure source material.

The aluminum chloride-containing effluent source material which suitablycomprises the residual hot gaseous effluent of the chlorination ofsodium contaminated alumina may also contain chlorine, phosgene andcarbon monoxide and dioxide, is of such character that, at a temperatureof between about 150°-250° C., it is contacted directly within suchfluidized bed of solid particles of aluminum chloride to directlydesublime thereon and thereby endow the bed with a self-replenishingcharacter as well as providing for production of aluminum chloride ofselective size and configuration providing advantageous handling andflow characteristics. More particularly, such aluminum chloride willhave an average particle size distribution of about 40-350 mesh, andpredominantly about 100-350 mesh. The herein described fluidized bedcondensation or desublimation process leads to an acceptably fine solidaluminum chloride product at a low level of cooling energy which isparticularly suited, especially because of its particle size,configuration, and purity, for direct utilization in the electrolyticproduction of aluminum metal.

Advantageously, the residual gaseous mixture that remains after thedirect desublimation of the aluminum chloride values has been effectedand which will normally be constituted mainly of carbon monoxide andcarbon dioxide along with small amounts of hydrogen chloride, carbontetrachloride, phosgene and chlorine, may be recovered as effluent fromthe fluidized bed and portions thereof may desirably be recycled asfluidizing gas for the bed of aluminum chloride particles.Alternatively, any suitable substantially dry and non-reactive gas suchas nitrogen, methane, air, carbon dioxide and/or carbon monoxide may beused to fluidize the bed.

The use of markedly low ambient desublimating or condensing temperaturesin comparison to the solidification temperature of aluminum chloride,e.g. 30°-100° C. as compared to 180° C., and the agitation inherentlypresent in the fluidized bed of particles of aluminum chloridesurprisingly results in the formation of a preferred range of size ofparticles as compared to that developed by desublimation atsubstantially higher temperatures in the vicinity of the actual ambientcondition solidification temperature of aluminum chloride as well asselectively contoured particles of generally lobular configurationcharacterized by the substantial absence of generally planar exteriorsurfaces. Since such configuration and range of particle sizescontribute to easy handling for subsequent electrochemical conversion ofthe aluminum chloride to metallic aluminum, the use of desublimationtemperatures well below the upper-ambient limits thereof according tothe principles of this invention is highly advantageous. Thus, rapidlyquenching the gaseous aluminum chloride in the fluidizing bed from atemperature of about 150°-250° C. to below 100° C., and preferably toabout 60° C., in a single stage or step, one would not have expectedthat readily handled and flowable particles of selective size andconfiguration would form.

Thus, by careful selection and control of the temperature ofdesublimation, and by using a fluidized bed of aluminum chlorideparticles in the condensation zone, it has been found that particles ofselective configuration are produced and that the particle size of thesolidified aluminum chloride can be selectively controlled. At lowertemperatures within the specified range of about 35°-100° C., theaverage particle size of the desublimed product is generally smallerthan those obtained at higher temmperatures within such range. Dependingon the particular temperature chosen, the aluminum chloride particlesrecovered will have an average particle size of about 40 to 350 mesh,and predominantly about 100-350 mesh. Operating temperatures of lowerthan about 35° C. for the fluidized bed are generally uneconomic andundesired since excessive coolant costs are necessitated and excessiveamounts of titanium tetrachloride when present are condensed out of theeffluent together with an increased amount of fines of aluminumchloride, whereas temperatures above about 100° C. under thecontemplated operating conditions result in an undue amount ofincomplete desublimation of the gaseous aluminum chloride andundesirable loss thereof in the gaseous effluent, considering that aportion of such effluent gas is separated, usually continuously, fromthe system for scrubbing out the obnoxious and/or toxic substancestherein.

For example, even at a relatively low temperature of about 90° C., ascompared with an aluminum chloride solidification temperature of about180° C. at 1 atmosphere absolute and of about 150° C. at about 0.5atmosphere absolute, a certain amount of the gaseous aluminum chloridevalues will not desublime since the vapor pressure conditions in thefluidized bed favor retention of a portion thereof in the gaseous state.In this regard, under the ambient conditions of about 0.5 atmosphere,the vapor pressure of AlCl₃ is 1 mm at 100° C., 0.32 mm at 90° C. and0.004 mm at 60° C., which confirms the desirability of usingcondensation temperatures at the lower end of the stated range of35°-100° C., especially where lower ambient pressures are employed.Naturally, the presence of other volatile or gaseous materials mixedwith the aluminum chloride may modify somewhat the aluminum chloridepartial pressure in the system and thus the condensation temperaturethereof.

In accordance with one aspect of the invention, the gaseous aluminumchloride-containing effluent is introduced into the fluidizing bedchamber, through an inlet maintained at a temperature above thecondensation temperature of aluminum chloride under the ambientconditions and preferably in the range of about 180°-250° C. Such inletis also so located that the gaseous aluminum chloride is introduced intothe bed at a location remote from any contact surfaces in or of thevessel as for example, on cooling surfaces or the like, to preventundesired or premature condensation of the gaseous aluminum chloride toliquid or solid phase at the inlet and at any such contact surfaces.Such premature condensation would soon lead to deleterious scaleformation and a layered build-up of hard coating of solid aluminumchloride on the vessel walls as well as on any cooling surfaces in thevessel and even in the inlet entrance. This would not only constitute aloss of valuable product but also would lead to a relatively rapidplugging of the inlet entrance, and obstruction of the usable vesselspace and insulating deterioration of the necessary cooling surfaces.Such undesired deposits would be difficult to remove yet without theirremoval inefficient heat exchange cooling, decrease in usable vesselspace and possible plugging of the inlet entrance would eventually beeffected.

The above noted problems involved in effecting the condensation ofrelatively pure gaseous aluminum chloride directly to solid form in asingle stage are not generally encountered in condensation of othermaterials in a fluidized bed. For example, materials such as phthalicanhydride which are condensed in a fluid bed are soft enough to abradeaway from any given contact surface of the condenser vessel under thescouring action of the moving fluidized particles. Thus, in the instantsituation the temperature, vapor pressure and locus of desublimationmust be controlled to avoid premature and detrimental condensation ofthe gaseous aluminum chloride to liquid form and at locations other thanthat heretofore described to effectively avoid agglomeration of the bedparticles and eventual failure of the bed, clogging of the inletentrance and deposition on cold surfaces of the chamber. Likewise, thegaseous effluent should comprise relatively pure aluminum chloride,since of course, any significant impurity content, e.g. of sodiumaluminum chloride as a complex mixture with aluminum chloride, if notremoved from the intended influent before it reaches the inlet entrance,would soon clog such entrance as a collected liquid condensate thereatdue to its relatively higher condensation temperature as compared withthe relatively cool environment of the chamber.

While normally the gaseous aluminum chloride-containing carriersubjected to the condensation fluidized bed treatment according to theinvention will be the gaseous effluent recovered from a chlorinationreaction of the foregoing type, such carrier can be effluent from adifferent type chlorination procedure or reaction or can be a gaseousaluminum chloride containing carrier supplied from any convenientsource, so long as the particular carrier is substantially free fromundesired contaminants which would detract from the intendeddesublimation step.

As illustrated in the drawing, an aluminum chloride containing gaseouseffluent from a chlorinator 1 is initially passed through purificationapparatus 2 wherein entrained particles and condensable volatileconstituents that condense above the upper ambient conditionsolidification temperature of aluminum chloride are removed. Theresidual gas which will be at a temperature that is sufficiently high topreclude condensation of aluminum chloride therefrom under the ambientcondition is introduced through the feed line 3 into a fluidized bed ofparticles of aluminum chloride disposed within a chamber 4. Thefluidized bed condenser chamber 4 includes a fluidizing gas distributioninlet 12 at its lower end supplied with fluidizing gas through line 11.A separator 21, suitably a permeable filter medium 23 and a residualgaseous effluent outlet 13 at its upper end connected to an outletconduit 14 and an aluminum chloride outlet 16 at the dependent terminusof an inclined or sloped perforated distribution plate 5 disposedadjacent the bottom of the chamber for directing the heavier particlestoward the outlet for effecting withdrawal of condensed aluminumchloride solids therefrom are also included therein. Examplarly disposedwithin the upper portions of the illustrated fluidized bed is a heatexchanger such as finned coils 10, for cooling the contents thereof andfor maintaining the temperature of the bed within predetermined ranges.The purified residual gas exiting from the purifier 2 and containing thegaseous aluminum chloride values is introduced into the fluidized bed ata location remote from the cooling fins and from any contact surfacestherein.

A residual gaseous effluent recycle conduit 17 is connected intermediatethe residual gaseous effluent outlet conduit 14 and the fluidizing gasdistribution inlet 12 to permit the recycling and use of portions of theresidual gaseous effluent as fluidizing gas. For such purpose, acompressor or pump 18 is desirably interposed in the outlet conduit 14.Alternatively, an independent source of fluidizing gas can be fed viasupply line 19 for fluidizing the bed, instead of or in addition to theresidual effluent gas fed via recycle conduit 17. Where the recycleconduit 17 is employed for supplying fluidizing gas for the system, suchgas of course will contain mainly carbon dioxide and carbon monoxide andperhaps some residual amounts or traces of unreacted chlorine, hydrogenchloride, phosgene or carbon tetrachloride, since it represents thefinal off gas residuum from the chlorination reaction. A portion of suchoff gas is removed via line 20 and scrubbed to remove obnoxiousconstituents before discarding. When an independent source of fluidizinggas is used, all of the off gas is normally removed via such line 20.

More specifically, this off gas removed from the closed system at line20, containing predominantly chlorine, hydrogen chloride and phosgene asobnoxious and toxic constituents must be cleaned before the gas can bevented to the atmosphere. Thus, the off gas can be scrubbed of theseconstituents with caustic, e.g. sodium hydroxide, or with sodiumcarbonate, etc., in the conventional manner, and then be vented.Furthermore, the gas can be burned in a furnace with hydrogen (or asource thereof, such as methane) to produce hydrogen chloride from thechlorine and phosgene, followed by scrubbing of the so-treated gasbefore venting or any other conventional method of removing theseobnoxious and toxic constituents from the off gas can be utilized.

In accordance with a further feature of the invention, the inlet 15 forthe gaseous aluminum chloride-containing gas is provided with means tomaintain the temperature of the incoming gas at an elevated value, suchmeans shown schematically at 24, may suitably comprise auxiliary heatingmeans, such as electrical resistance heating means, or may comprise heatinsulation material, such as quartz, alumina, graphite, asbestos and thelike, at the entrance thereof to minimize, if not prevent, prematurecooling and liquification or solidification of the gaseous aluminumchloride passing therethrough which would tend to clog the same toimpede or otherwise deleteriously affect the desired condensation ordesublimation operation. Thus, the means for controlling the temperatureof the inlet gas contemplated herein will function to permitintroduction of the flow of gaseous aluminum chloride-containing fluidsubstantially without loss of heat into the interior of the fluidizedbed.

Because of the need to avoid premature condensation of the gaseousaluminum chloride at locations other than in the fluidized bed itself,considering the ambient conditions, the entrance of inlet 15 desirablyprojects appreciably into the bed and terminates remote from all contactsurfaces therewithin including the walls of the chamber and the coolingmeans 10. In this way, as the incoming gaseous chloride-containingcarrier enters the condenser chamber 4 in such manner as to immediatelycontact the bed particles and the aluminum chloride values therein willcondense before there is any chance of contact thereof with the adjacentapparatus surfaces. By the time the mixture of residual gaseous effluentand fluidizing gas exits from the top of the bed, the aluminum chloridevalues therein have sufficiently changed to solid phase and built up insolid particle form to avoid significant entrainment in the exitinggaseous mixture and are heavy and hard enough to operate as a particlecomponent of the fluidized bed into the vicinity of the chamber wallsand cooling means without danger of deposition thereon.

The ambient conditions at the locus of condensation should be such thatthe vapor pressures of the aluminum chloride is just low enough todesublime the same to solid form without causing any deposition ofresidual aluminum chloride either in solid or liquid form on the surfaceof the permeable filter medium 23 of the separator 21.

The singular nature of the product resulting from the hereinabovedescribed direct desublimation recovery of aluminum chloride values isillustrated, under various magnifications in FIGS. 2 and 3 of thedrawings. As best shown in FIG. 2a (under 30× magnification) theparticles of aluminum chloride are of generally spheroidal characterpresenting a generally lobate curvilinear external contour andcharacterized by a marked absence of planar exterior surfaces andrelatively sharp protuberant angles that are normally characteristic offracture planes or the like. As becomes apparent from FIGS. 2b and 2cthe particles of aluminum chloride are compositely constituted ofagglomerated, cemented or otherwise autogeneously bonded pluralities ofsmaller sized particles of rather widely varying dimension but ofgenerally spheroidate character. Because of such composite constitutionthe exterior surfaces of the particles, while still curvilinear incharacter, are of generally lobular and bullate character and presentmarked localized departures from true spheroidal character and hence theterm "lobular" will be herein hutilized to describe the generalcharacter of the resultant particles.

FIG. 3a illustrates (under 30× magnification) a much finer aluminumchloride product obtainable by the practice of this invention. Asevidenced by FIGS. 3b and 3c however the particles here are of markedlymore lobate character. It is equally apparent however that the particlesagain present a generally lobular curvilinear external contour and arecharacterized by a marked absence of planar exterior surfaces andrelatively sharp protuberant angles and are compositely constituted ofagglomerated or otherwise joined pluralities of smaller sized particlesof widely varying dimensions but of spheroidate or lobate character.

The solid lobular aluminum chloride particles of generally curvilinearcontour of the invention essentially contain rounded lobes or lobuleswhich often impart an apparent bullate, blistered and/or nodularcomposite surface configuragtion.

As will now be apparent to those skilled in this art the generallylobate character of this product differs markedly from conventionallyproduced aluminum chloride that is commercially available. Not only doesthis new material provide marked advantages in both handling andflowability but the herein described invention avoids any crushing orgrinding operation with their attendant contamination with impuritiesfrom the equipment employed but more significantly avoids exposure ofthe aluminum chloride product to the air with its ever attendant hazardof contamination by air borne moisture.

The new product obtained through the practice of this invention has abulky density in the range of about 75 to 105 lbs. per cu. ft. (for aparticle size range of from about 40 to 350 mesh). Samples of FIG. 3type product have been found to have an angle of repose in the range ofabout 35° to about 41°, and a mean of about 38°, when measured in a drynitrogen atmosphere by the International Standards Organization MethodISO/PC 47 (Secretariat 247) 424 for measurement of the angle of reposeof alumina. Because of the greater spheroidicity of the FIG. 2 typeproduct lower angles of repose will normally be characteristic thereof.As a matter of caution however, it should be noted that values for theangle of repose depends largely upon the measurement techniques employedand there is little, if any, standardization in such measurementtechniques generally, and the requirement of maintaining this particularproduct in a contaminant free environment further complicates theproblems of measurement thereof.

EXAMPLE

The following example is set forth to illustrate, without limitation,various features of the present invention.

Carbon impregnated or coked porous alumina particles were chlorinated atelevated temperature and the resulting gaseous reaction mixture treatedto remove entrained particles of solids and liquids and condensablevolatile impurities which condense at a higher temperature than thecondensation temperature of aluminum chloride under the ambientconditions, so as to provide a relatively pure gaseous effluentcontaining essentially only aluminum chloride, carbon dioxide and carbonmonoxide as well as trace amounts of other impurities, e.g. chlorine,hydrogen chloride, phosgene, carbon tetrachloride, and the like.

Such relatively pure gaseous effluent at about 200° C. entered thedesublimer or condenser chamber 4 shown in the drawing via the heatinsulated inlet 15 at a rate of about 885 cubic feet per hour. Condenserchamber 4 on the average contained a bed of about 90 pounds ofrelatively pure aluminum chloride solid particles of an average sizedistribution of about 40 to below 100 mesh maintained in fluidizedcondition by passage of fluidizing gas (i.e. dry air) via line 19upwardly through distribution inlet 12.

The heat exchanger 10 was cooled by passing water at about 20° C.through cooling coils so that the average 200° C. inlet gas enteringthrough feed conduit 3 was quenched to about 60° C. on the relativelypure aluminum chloride particles maintained in the fluidized bed.

The quenched or cooled gaseous aluminum chloride apparently formed solidnuclei particles which built up to larger particles and/or deposited onother solid aluminum chloride particles already present in the bed. Asthe particles of aluminum chloride increased in size, they were removedconstantly from the bed via outlet 16 and in an average particle sizedistribution as noted above. Under the specified conditions noappreciable or troublesome deposition of condensed aluminum chlorideoccurred either in the heat insulated inlet nor on any contact surfaceswithin the chamber, i.e. including the chamber walls and the coolingcoils.

The off gas from the fluidized bed maintained in condenser chamber 4 waspassed through the filter assembly 21 and the separated entrainedaluminum chloride solids and dust were returned directly back to thebed. Such off gas contains primarily carbon dioxide, carbon monoxide andair with trace amounts of unreacted chlorine, hydrogen chloride,phosgene, carbon tetrachloride and the like.

The aluminum chloride product recovered at a rate of 72 pounds per hourvia outlet 16 was a relatively fine solid product of generally lobateand spheroidate character as described earlier, having less than about0.3% by weight total content of combined oxygen impurities, a lowcontent of adsorbed carbon dioxide and phosgene (trace amounts), anaverage particle size distribution of:

    ______________________________________                                        +40 mesh (retained                                                                               8%                                                         100 mesh          22%                                                         (passes through)  40%                                                         ______________________________________                                    

and a density of about 75-105 lbs./ft.³.

What is claimed is:
 1. Process for the recover of aluminum chloride froma gas containing gaseous aluminum chloride, comprising the steps ofdesubliming said gaseous aluminum chloride on particles of aluminumchloride in a self-replenishing fluidized bed thereof maintained byintroduction of substantially aluminum chloride free gas at the lowerperimetrically defining boundary thereof and at a temperature below theupper ambient desublimation temperature of aluminum chloride introducinggaseous aluminum chloride at a temperature above the upper ambientdesublimation temperature thereof into the said fluidized bed at alocation remote from the locus of introduction of said substantiallyaluminum chloride free gas, and removing selectively sized flowableparticles of aluminum chloride from said fluidized bed.
 2. Processaccording to claim 1 wherein the fluidized bed is maintained at atemperature of between about 30°-100° C.
 3. Process according to claim 1wherein the fluidized bed is maintained at a temperature of betweenabout 50°-70° C.
 4. Process according to claim 1 wherein the desublimedaluminum chloride removed from the bed has an average particle sizedistribution of about 40-350 mesh.
 5. Process according to claim 1wherein the fluidized bed is maintained at a temperature of betweenabout 30°-100° C. and the incoming gaseous effluent is at a temperatureof between about 110°-250° C., and wherein the thereby desublimedaluminum chloride is recovered in an average particle size distributionof about 40-350 mesh.
 6. Process according to claim 1 wherein at least aportion of the residual gaseous effluent exiting from the fluidized bedis recycled as fluidizing gas therefor.
 7. Process according to claim 1wherein the gaseous aluminum chloride is introduced into the fluidizedbed through an inlet maintained at a temperature above the upper ambientsolidification temperature of aluminum chloride to minimizedesublimation thereof at such inlet.
 8. Process according to claim 1wherein the gaseous aluminum chloride is introduced into said bed at alocation remote from any contact surface to minimize desublimationthereon.
 9. Process for the recovery of solid aluminum chloride from agaseous effluent containing such aluminum chloride in a gaseous state,comprising the steps ofmaintaining a fluidized bed of particles ofaluminum chloride having defined upper and lower boundaries byintroduction of substantially aluminum chloride free fluidizing gasadjacent the lower defining boundary thereof, maintaining said fluidizedbed of particles of aluminum chloride at a predetermined temperaturesubstantially below the upper ambient solidification temperature ofaluminum chloride, introducing said aluminum chloride containing gaseouseffluent at a temperature above the upper ambient solidificationtemperature of aluminum chloride into said fluidized bed of particles ofaluminum chloride intermediate the upper and lower boundries thereof andremote from any contact surfaces perimetrically confining said fluidizedbed or disposed therewithin to selectively desublime said gaseousaluminum chloride remote from said contact surfaces and effect acontinued growth in the size of said particles of aluminum chlorideconstituting said bed, and selectively removing flowable and largersized particles of aluminum chloride from adjacent the lower boundary ofsaid fluidized bed.
 10. Process according to claim 4, further comprisingthe step of cooling the self-replenishing fluidized aluminum chlorideparticle bed through cooling means disposed within the bed.
 11. Processaccording to claim 5 wherein the fluidized bed is maintained at atemperature of between about 50°-70° C.